More specifically, the apparatus is of the type described in U.S. Pat. No. 4,576,211. The apparatus described in the patent comprises several mutually mobile constituent parts. At one end it contains a seat into which the end of a syringe can be fitted so that its needle extends into a closed chamber bounded by the apparatus, and at its other end it comprises a seat for housing the mouth of a bottle containing a medicament. The various constituent parts of the apparatus can move axially along each other to securely lock the bottle mouth in its seat by means of retention teeth projecting from flexible tongues. Additionally, the axial motion of the various constituent parts of the apparatus causes the point and a portion of the needle to emerge from the chamber in the apparatus so that the needle can perforate an elastic plug fitted in the bottle opening and can penetrate into the bottle, to be able to inject into the bottle liquid contained in the syringe or to draw into the syringe liquid contained in the bottle. While the bottle is connected to the apparatus, the needle is always contained within the apparatus chamber or (party) within the bottle--i.e., the needle is never freely exposed and accessible from the outside.
The apparatus described in U.S. Pat. No. 4,576,211 has, however, the drawback that, if no bottle is inserted into its seat in the apparatus, the apparatus can still be erroneously or accidentally operated in the sense of moving the various component parts along each other to cause the needle to emerge from its protection chamber. In such a case, the needle would project outwards from the apparatus and be accessible from the outside, with consequent danger in terms of loss of needle sterility and even greater danger if a high-risk medicament such as an antitumoral drug has already been drawn into the syringe.